Systems using consumable fluids often rely on intermittent storage in fluid enclosures. State conditions of a fluid enclosure, such as the state of charge, provide information to predict and assess the needs of the system responsive to fluid exchange with the fluid enclosure. For example, in systems using replaceable or refillable fluid enclosures, state conditions can be used to predict the amount of operating time left before the consumable fluid supply may be depleted.
Often, sensing components or system peripherals for determining state conditions are in physical or mechanical contact with the enclosure. However, removal or replacement of fluid enclosures from systems using contact-based sensing may be cumbersome. In addition, the accuracy of state condition measurements and the lifetime of contact-based sensing devices may be compromised when used for fluid enclosures that are exposed to abrasive environments.
One example of a fluid enclosure utilizes metal hydrides for hydrogen storage. Metal hydride fuel storage systems are attractive candidates for use as refillable fluid enclosures to store fuels, such as hydrogen, in conjunction with fuel cells for electrochemical generation of power. However, metal hydrides undergo thermal cycles during absorption and desorption of hydrogen. As a result, determining state conditions for metal hydride systems becomes especially difficult.